Sound amplifier muting means



Aug. 29, 1950 E. F. M DONALD, JR

SOUND AMPLIFIER MUTING MEANS 2 Sheets-Shea Filed Sept. 26, 1945 Fi'g. 9

Fig. I0 204 I97 22 INVENTOR. m M

3W Hrs ATTORNE Ys Aug. 29, 1950 F, MCDONALD, JR 2,520,732

SOUND AMPLIFIER MUTING MEANS Filed Sept. 26, 1945 2 Sheets-Sheet 2 AMPLIFIER Fig.2

Osc. Moo.

STAGES EUGENE E MCDONALD JR.

- UN 3 INVENTOR. 1: w 1 x 5 BY WfiSGw- LL 1 E M5744.

.p v- H/s Arron/vars atented Aug.

' 2 520,73 r I soU'ND AMPLIFIER. MUrInMEAN-s Eugene McDonaliilrlyQtliicago, Ill p Application September 26, 1945, Serial No.- 618358 40laims. (longed-ism T" The present invention relates to radio receivers,

sound amplifiers and the like and, in particular, to a system and means for silencin apparatus of that type for a predetermined time interval.

In listening to the reproduction of sound from a radio receiver, a sound amplifying device, phonograph, recorder, .etc., it may be desirable to control or interrupt the sound transmission for .a.predetermined time interval as, for example, when riding in an automobile and listening for "train whistles or bells at a railroad crossing, when iconversing with other persons or when undesirable sounds are emitted from suchapparatus. in such cases it is desirable to effect such a control with ease.

Itis therefore an object of the present inven- ;tion to provide a novel control for apparatus of .-;the type specified in which the apparatus maybe ;silenced easily and automatically for a predetermined time interval. The type of control contemplated in the pres- :ent disclosure is particularly applicable to pres- ;ent day broadcast receivers over which repulsive iadvertising matter of an annoying nature is stransmitted. When applied tosuch receivers it is. desirable that the control be automatic in ;.operation to restore the receiver to. fully opera.-

. :tive condition after the duration of such advertising matter,

Another object of the present invention is to provide a novel arrangement in which a radio receiver may be squelched for a predetermined time interval, approximately twenty seconds, .commensurate with the duration of an average icommercia of advertisingmatter- The present control finds great applicabilityin automobile radio receivers which are controlled at or near the floor board of an automobile in accordance with. the teachings in my prior pat- .ents. In such .case an operator need not hold the control down for a prolonged period of time as in my prior Patent No. 2,374,873,.granted May 1, 1945, but need only touch and release a button in which case the receiver is squelched andis then restored automatically to fully operative condition after a predetermined period of time without requiring the attention of the driver whose at .tention, of course, for the purpose of safety, is

needed elsewhere.

Still a further object of the present invention isto provide a novel muting arrangement in the control shown in my above mentioned prior patent.

The features of the present invention which are believed to be novel are set forth with particularity in: the appended claims. The. present. invention itself, both as to its organization and manner of operation, together with further objects and advantages thereof, may best be understood by reference to the following descripproducing a delaying action shown in Figs. 1-5,

tion taken-in connection with the accompanying drawings in which; 7 I H Figure 1 shows a part of the interior of anautomobile in which apparatus incorporatinglthe present inventionis mounted; Eig.;2 shows structural and schematic circuit arrangements incorporating the control appaatus shown in Fig. 1; V

Fig. 2A shows a fragmentary sectional view of a portion of the apparatus shown in Fig. 2; f Figs. 3-5, inclusive, show enlarged fragmentary sectional views of apparatus in Fig. 2 in diiferent operating positions;

H Figs. 6-8, inclusive, show preferred modified apparatus in difierent operating positions thereof for practicing the present invention, and

. Figs. 9 and 10 show other modified structures for practicing the present invention.

This invention is particularly applicable to maintain a radio receiver silent for a predeterminedperiod of time after actuation of a control which incorporates inherent means to restore the receiver to fully operative condition aiter'a predetermined time interval. In accordance with the present invention, the control may accomplish the desired result by producing a delaying action either by electrical means as shown in Figs, 1-5, inclusive, and Fig. 9, or @by mechanical means as'siiown in Figs. 6-8, inclusive. Also,

in accordance'with the preferred embodiment of the'invention, for saietys sake, the control is maintained on the floor board in an automobile where it is readily accessible for foot operation by the operator of a moving automobile without the necessity for him to remove his hands from the steering wheel, but it will be apparent that the control shown may be mounted elsewhere in an'automobile, for example, on the steering post in a position accessible for operation by the knee or leg of the driver. Furthermore, itwill be apparent that the apparatus shown herein may be mounted elsewhere than in an automobile, for example in a household receiving system whereit will function equally well.

Referring to the electrical arrangement for inclusive, the control having the general referencenumeral I is mounted on the floor board 2 of an automobile where it may be actuated easily by the driver without either removing his hands from the steering wheel or taking his eyes off the road. i

The control I functions not only to produce muting, station changing and volume controlling of a radio receiver having the general reference numeral 3 as shown and described in my prior Patent 2,346,177 granted April 11, 1944, but serves also to produce what 1 term delayed mutin By delayed muting in this specification and ermi is understood that no reference is made to the ordinary type of clock control but reference is made to silencing or partly silencing, by actuation of a single control, the transmission of sound for a predetermined relatively short time interval after which interval thesinglecontrol assumes its normal position and condition and sound transmission is automatically restored without manipulation of another or the same control, the restoration of sound transmission being accomplished by utilizing energy which is simultaneously either stored or""applied"in 're'-' sponse to actuation of suchsingle. control in yetfecting the action of silencing or partly silencing.

Referring specifically to Fig. 2, the receiver3,' tuned by the tuner having the general reference numeral 4; is arranged to receive signals 'on antenna 5 and to reproduce the sound components in speaker S, the volume of the sound compor'ints being controlled by volume control resistance 55 incorporated in the'co'ntrol I which has foot control knob 8 arranged to be rotated for volume control purpos'es'"and to be moved longitudinally for delayed muting, muting and station changing.

The receiver is tuned by inductance coils 9, III, each'of which has an inductance value 'determined respectively by the'relative positions of the tuning cores II, I2, the tuningcores being psitioned by the tuning'mecl anisin describedpres- The tuner 4 is of the so-called turret tuner type "and tuningmay be accomplished ina'progressive sense by turning 'manualtuning knob I3 which may be journ'aied for rotation ats'ome convenient place, for example on the'dashboa'rd I4 ofth'e automobile. "As will *be' seen presently, the knob is serves notonly'to produce so-calied continuous tuning but's'erves also to'adjustthe turret tuner for so-calledsequential tuning. Such sequential tuning of'the'associatedre ceiving apparatus may be effected by sequential operation of the control Icontrolled by-thedriver of the automobile. That is, the "arrangement ilflustrated" infig. '2 tunes the radio apparatus; of which t g u anqe 'fl and ."a f."? "i art either upon'actnationpf themanuartuning knob "I3"or the control "I *which' servesto close "and 'opena switch I'comprisin'g contactsflli, If'I.

"The inductanceso'fcrils il and Itiieterinine the frequency 'of'the received 'si nalsfandthese 'in- "ductances are'varied respectively, by adjusting the position of tuning cores Ii'and 12 of'relajtlvely high permeability with respecttof coils 3 and It. Only twotuned'inductance coils are shown in Fig. '2 'for simplicity, but itshould 'be understood that more "than two, and preferably three or four of such"coils,'are tunedsimultaneously by positioning relatively high permeability members similar to members-1 I and I2 with respect to inductance coils which are connected in the radio receiving apparatus. The tuningmem bers or control-members, such'as members-11 and I2, are carried on a movableca rria'geia, which is secured upon a rod i9 con'nected to a movablesolenoid core' 26. The rodIS has its forward end 2! built soas to cooperate w-ith- 'one of a plurality of stops or abutments not the tiirret assembly 23 "-andtheshtOpsZQ-are adjustably held in the turret assembly '23 by cooperatinfg screw threads on stops 22-and *mr'r'emssembly23'as shown in cletailin Fig. 2A.

The *turr'et assembly 2 3 is 'secu'red' upon a rotatable shaft 24 which-carrisa ratchet' wheekfi with a'pawl 25 so astorota-te*the shaft "Z4 one step or one sixthof-arevdlution for each 4 reciprocation of the pawl 26. The pawl 26 is piv otally mounted on an arm 27 which swings about the shaft 24 and. is pivotally and slidably connected to one arm or" a bell crank 28 having its other armpivotally arid'slidablyfqonnected to a lever member 29', the latter being pivoted on a. fixed pivot pin 36. The lever member 29 extends from its pivot pin 30 and has a slot 32 to accommodate a pin 33; secured upon the rod I9. The upper end of the lever 29 is preferably positioried so as to be visible and cooperates with the scale 35 having suitable graduations thereon whereby a suitable indication of the position of rod I9 and tuning members II and I2 is obtained.

"With the apparatus 'thus far vdescribedin Fig, 2, it is 'cl'earth'at when rod I9 moves to the left in thedirection of itsaxis, the bell crank 28trotates behind 'anadjacent tooth on the ratchet wheel .25,"and that'when'therod I9 returns'to'th'e right the ratchet wheel is rotated onesixthof a reveolution to a position where an adjacent stopin on turretassenibly 23 limits furthermovement ofthe rod I9 and inductancatuning members II "and I2 carried thereon. The manner in which the solenoid core .20 and associated rod 19 are actuated upon energization ofithe associated solenoid 35 is described now.

When solenoid 35 is energized, for example by producing a current fiow throughthe'switch I5 comprising contacts i5 and I1 and described in detail'later, solenoid'core 20 and rod'I9 are moved to the left in Fig. 2 to a position where'switc'h contacts 36, 31 of switch-38 are in'circuit closing position. Upon deenergizationof' the solenoid by allowing switch contacts I6; I? of switchiI's to assume its normally opened position, the solenoid core 20 is returned to 'its i'urthermost position to the right in Fig."2'under the influence of tension spring 39 havingone ofits ends'fastened'tothe levermember 29 and its other end fixed on, for example chassis fifl, after pawl 25 has turned the turretassem'bly"23"an' angular distance cor-'- responding to the angular distancebetweenadjacent stops In summary, when solenoid 35 is energized due to currentflowing therethrough and through switch I5 from voltage "source 74I, solenoid IBL- i's moved to'the leftia'gainst the action'of tension spring 39, and the pin'on'rod I9 engages lever '29 which pivotsrab'out its pi'v'totpin :30 so as' to rotate the bell crank 23' counterclockwise around'.-its pivot member. whenand' asibell crank 28 moves thus counterclockwise, the arm" pivotally. mounted .onshaft 2,4.and having=piizotallyimounted1thereon pawl 26 rotates counterclockwise :aboutiits sup.- portingshaft 24a distance somewhat greater thanoneesixth of a -revolution.so as toallow pawl -26 to drop behind and engage anadjacent tooth on ratchet wheel 25. When solenoid 3.5 :isdeenL- sized clue to th open n of s t h J1 tension spring 39 causes clockwise movement of the lever arm 29 and causes the turret assembly 23 to be moved an angular distance correspondingto'the angular distance between teeth on ratchet=wheel 25', which distance correspondsto the angular distance'betweenstops '22;

Stops 22 are adjustably mounted in turret mem- 'ber23 andthe relativeposition of each particular It is thus clear that when foot operated. switch l5, which is connected in a series 'circuitwith voltage source 4| and solenoid 35, isclosed, solenoid 35 draws the core 2B.to the leftiand causes the arm 21 to rotate one step corresponding to the angular distance between stop members.

Therefore, in order to tune the receiver by actuating the foot operated switch l5, it is necessary that the switch l5 be sequentially closed and opened until a particular stop 22, corresponding to a desired station, limits movement of rod l9; whereas, when it is desired to tune the receiver continuously over a range, the manual tuning knob I3, preferably located on the dashboard, is rotated. For the purpose of providing continuous-tuning, as well as providing an adjustment for the stops in the turret assembly; the knob 13 is coupled to gear 42 through shaft 43. Gear 42 is arranged to engage at least one of the stop gears 44 which, as shown in Fig. 2A, is threaded in stop assembly 23 and is confined within a hollow portion of turret assembly 23 by the walls 45 and 46. Conventional means, not shown, are provided to prevent rotation of stop 22 when gear 42 is turned. When knob l3 is turned manually, the stop 22 is turned in or out'of the turret assembly 23 in a direction depending upon the direction of rotation of knobl3; and rod 19 which is pressed against stop 22 by tension spring 39 follows the movement of the stop member '22. The position of rod I9, as explained previously,

, determines the inductance of coils 9 and I9 and hence the tuning of the receiver.

*In addition to serving as a manual-tuning means, the knob l3 may be turned to adjust the position of the other stop members 22 in turret assembly 23 so that all of the stop members 22 may be in suitable position for tuning when the denser 53A is connected in shunt to serially connected resistances 53 and 55 for bypassing currents of superaudible frequency. The volume control resistance 55 has its variably positioned tap connected to grid 56 through lead 54B'and through coupling condenser 51 to supply 'a'selected fractional portion of audio frequency voltage detected in diode 5|, 52 and appearing in the previously mentioned serial circuit across leads 54A, 543 to the amplifying section of the diode-triode device 58 comprising the diode ele-' ments 5|, 52 and the triode elements 52, 56 and 59-thetriode anode. I I 1 The triode 52, 56, 59 is supplied with space circuit through load resistance 59A from source 60 having its positive terminal connected to anode 59 and its negative terminal grounded. Amplified voltages appearing on anode 59 are transferred to another audio frequency amplifier stage 61 through coupling condenser 62. I a

' The amplifying characteristics of the amplifying circuit including triode 52, 5'5, 59 may be controlled in a manner described-presently to prevent for a predetermined time interval the transmission of detected audio frequency voltage from leads 54A, 543 to the amplifyingstage 6|.-

It-is-noted that the grid 56 is connectedto' ground through'a grid leak resistance 63 which has connected in shunt thereto a first series circuit comprising resistance 64 and condenser 65 and also in shunt thereto a second series circuit comprising decoupling resistance 66 and condenser 6! for performing a desired control operation; Condenser 9-1 is arranged to be charged with its ungrounded terminal at a potential sufficiently negative to produce stoppage of space current through the triode 52, 56, 59 and for thatpurpose the ungrounded terminal of condenser 6'!- is serially connected to the ungrounded negative terminal of voltage source 4lthrough the series circuit includinglead 68, normally open switch 69 having contacts 10, H and 12 and resistance 13. Condenser 14 having its ungrounded terminal connected to lead 15 connecting switch contact 10 to resistance 13 is not essential to the practice of the present invention in its broadest form, but is desirable as will be explained later to-obtain a predetermined timing interval regardless of the duration of contact between switch contacts'lO and H. Suffice it to say for the present that the presence of resistance 13 plays an im: portant role immediately after switch contact H is disengaged from grounded switch contact 12 but remains in engagement with switch Contact" 10 and thepresence of condenser 14 assures a predetermined timing interval upon closing of switch contacts 19 and H. v Resistance 54 and condenser 65 are not vitalto the practice of the present invention in" its broadest form but certain desired operatingadvantages are produced in that their presence insures quietness of operation of'the receiver when the core members II and I2 are in transit from their furthermost left position in Fig. 2 to their arrested position wherein rod extension 2! contacts one of the selected stop members 22: For'that purpose the ungrounded terminal of condenser 65 is connected to the ungrounded negative terminal of source 4| through the normally open switch 38 having the contacts 36 and 31. It is clear that in operation of the tuner 4 when switch 38 is closed condenser 65 is instantaneously charged to a negative potential assuring a cutoff. dfspace current in triode 52, 56, 59, and that after opening of the switch 38 the condenser 55 remains charged'and triode 52, 56, 59 remains inoperative to amplify signals for a time interval" depending upon the time constant of the circuitpermanently connected to condenser 65, such time constant being in the order of one-fifth second, a time sufficiently large to allow tuning cores ll, l2 to return from their extreme left position in Fig. 2' to their extreme right position to prevent undesirable noise'in the interim.

1 In the operation of the delayed muting switch 69, it is clear that when insulated switch contact 10 remains in its normal position in Figs. 2 and. 3 for a prolonged period condenser 54 assumes the potential of source Al and that thereafter when the insulated contact is moved downward to the position shown in Fig. 4-. wherein contacts 10 and H abut, the charge initially stored:- in condenser 74 is instantaneously distributed in condensers 14 and 61, condenser 6'! assumes a voltage sufiiciently negative to cut off the flow of space current in triode 52, 56, 59 and there'- after when theswitch contact i9 is allowed to return to its normal position shown in Fig. 1 the device 52, 56, 59 remainsinoperative to suitably transmit signals a timeinterval determined by the time constant. of .the circuit permanently.

anaemic connected to condenser 61; This tl'meiinterval is, preferably. of the order of: thirty seconds-and can be. controlled easily. by .-adjusting "thennagnitude of condenser 61.

In case. it isdesired to. terminate the action-of delayed vmuting once ithas been initiated; switch contactll, is moved tothe. position, shown in Fig. 5; wherein insulated contact in is in=contact with spring contact H andflexeslitmutwmdly to where it engages the contact -.l2.which in reality istheinner wall of the grounded control housing. Switch contact H is sufficiently-flexible toserye this junction without interference in its fu nction produced-from spring 76; described later,- When positioned as shown in Fig. 5,,switch is serveseto sho itr n e e. har e herein dissipated and device 52; 5G,. SS-becom s immc iate y p ti o r s t i na N rmal y; hen the switch ur ms herosition hown nia-fi w the ition, bow ..in. ia 4,- and then. tothenormal position-shown in Fig; 3,, in order that the condenser J1 :may; not be char ed ppr c b y ng. he {moment when the switch is in the intermediate position shown in Fig, 4,. the resistance 13 is madeof sufilciently large magnitude to allow only anegligible amount of charge to flow into condenser 61, during such moment.

As an example, in one practical embodiment of the. present invention satisfactory, delayed muting action was obtained-when the triode ele ments52, 56., 59 were incorporated-ma so called discharge device of the type commonly known as the 7186, resistances 63, 64, 6S. and Jihad magnitudes respectively equal to 15, 1, 1 and l megohms and condensers 65, 61. and l'lhequal magnitudes respectively equal to ..02,2 and- 2 miorofarads.

Provisions are made also intheaitrangement shown in Fig. 2 to produce a muting actionby holding aswitch in circuit closingposition such muting action continuing until: the-switch ia allowed to assume its normallyopen position. For this purpose one terminal of thespeaker 6 is grounded and the. other terminal is connected to ground through the lead 11, switch 3| comprising the contacts l6, 83,; thedatten switch contact being grounded through the housing J01. control r The control 1, preferably arranged on board of an automobile but which may; .be-ar ranged at any other s ab .r a ai her amobile, for-example on the steering epostiorknee, finger or leg operation or on the dashboard,

for finger operation, includes not only the volume. control potentiometer. 55 butalso normally open switches 69, 8| and :5, all ofwhich, are closed. in that. order by depressing the .confirolknob 5 and areopened in reverse order,- whenandas the control knob 8 is returned fromits further: most depressedposition to its normal position;

Rotation of the control knob-.8 produces a change in settingof the volume controlpoten tiometer 55. The structural features-of confirm I for efiecting the above described controbar: rangements are described now. lngeneral the control I is constructed identically to the-cont; trol which I have disclosed in Fig. 6 of my prior; Patent 2,374,873, butis modifigedto incorporate the switch '69. for producing delayed mutingandfor stopping such delayed mutingat, any timgflte thewish of the operator.

spring member and. the contact l1 upon a contact. supporting strip. 88, Awafer-lilgg The switch contact. I6. iscarriedby a spiral] contacts assembly: 2|,- comprlsing sheets of insulatinmmaterlalnsand 93; issecured to the-bate piste. .-O r the switch by tubular rivets: or other suitableihstening. means 96; The rivets Stalso serve-insecure the sheetszsz' and 93 together so ante retain; the contact. strip 88: in. position between-:them; Anear 89 on the strip.il9..providesba terminalztowhich the conductor may be integrally. securedin-a permanently. conduce tive memberas byv soldering. or welding. The spiralsprine. member. '88:. is fastened; to thazins sulatinz sheet:

The cim-shapedjcontact .enclosing member". 184 is adaptedfor connection to the .base plate 9.4 .by eyeletsconnections HIE orother suitable securin The reciprocable and. rotatable cont ct 83 iSL'EllidBd-i for: longitudinar movement y: a guide-bushing. 1 B8 of. insulating. material which isqcri-moed; oan; aperture 7 located substantially concentricallymith the aperturesain the 5 contact upporting. members-1.88; and. 89; A .(HSOLOI'. washer IDS-nurroundethe rcducedportion H l or; the air: cularbodyofthecontaci:183.. Thespring 16 pre: sents :two substantially r fiat ends, one oil which rats, omthe; member 104, and the, other rests asainstitheswasher 109.: The. washer. l sslid'w bly; in 8-: ylindrical housing- I [6 which} has an inwardly turnedfiange H1. Outward movement of. the. washer l 83 isthus limited tothereby hold the spring; 16: partly; compressed. The housing Hlirmay; be secured to the top of the contact enclosureimemba I04 bywelding. its outward-1g turned flange I N to'the enclosure-member cylindrical sleeye 1 2i surrounds th reduced porticn-zll i the-contact and rests on the washer we... '.h.i .-sl eveiss ou ed: y h rsor mi i 23;wh i ch; 1s;lighter thanthe spring 16. The aperturaproyidedcat the'top of the housing HQ is large enough'to-accommodate the spring I23. 1; .i9mbm .d:0i erating=im0b an button comprjming the-,cup-shaped member H's-and; the an: nularmcmber 121, is riveted-ontothe :top oithe contact member 83- as indicated vb L reference character- 128: The. annular member 121. is knurledprptherwise formed to provide. a. rough: ened surface-as-indicated by reference charactfilj I29; southat .itxnay-v be rotated bythe fcotoi the person desiring-.-.-to;control the volumeof sound emitted-byline loud speaker '6 of the radio-re; ceiueri The cup-shaped member I25 overlaps thg-hoygjpgfl 1 .130. prevent dirt and-forei n mall-:- ter il'om enterhigtheswitch. After the me; chenicalconnection at point I28 is:--made,the springtlza -is helddn compression between combinedknob and button 8 and the washer I59.- Iheportion of the contact, WhiChgPY-Q'; video the permanent connection I28 is. prefer-,- ablysquare in cross. section-to fit a-squareapet ture in the-cap member I 25 thereby to insure r0 tatioaol -t econt t :83 w h m dope atingknob andjcuttom is rotated. It will; be un: clerstood that any irregular shapeinrcross section may ;-be,- =gifyten--tothe;portion of the con a tgn whichmrovidefi for the riveted connection for thapurpo-seoiinsuring rotation of the contact ajWfllh; the -;combined knoband button '8, Fe! that zpurposa; contact-member l0 1 is in, the form nfin lar; infl nsulated .from contact momloer 83 by means of insulation 10A. The switch cqsing is cqn ected toground. The movable'contact ,83 of, the switch-is electrically connected to tbegroundedbase plate. 94 through the-mom}; bersjM, H6, 19,123. and l25..

Upon exertion oi pressure onthe, combinedjop -I erating lmoband button a to. reciprocate. ts;

9 tact '83 toward circuit closing engagement with the contact I6,-'the top of the sleeve I2| is engaged by the inner surface of the combined knob and button following initial compression of the spring I6.

At this time the contact 83 is in full circuit .closing engagement with the contact I6, completing a circuit. from the speaker voice coil to ground by grounding the conductor 11 and thereby muting the speaker. At this point in its movement, th contact '83- has not brought the contact I6 into circuit closing engagement with the contact II. Further movement of the combined knob and operating button 8 causes the spring II4 to be compressed since there is now a direct connection between the knob and operating button 8, the sleeve I2I and the washer I09. Because of the added resistance of the spring II4, the operator can sense the point at which the circuit of conductor 11 has been closed and the closing of the circuit of conductor 62 is about to occur. Additional movement of the contact 83 will cause the contact I6, which is now grounded by the contact 83, to engage the contact I! to complete the circuit including the conductor 82.

The volume control section 55 of the control I includes a volume control rheostat described previously which may be of any well known type, adjustable by rotating its operating shaft I33.

The rheostat is shown as being secured to a bracket I34 by means of a nut I36. The supporting means for the rheostat just described is convenient since volume control rheostats are readilyavailable which are of the-panel mounted type shown, employing the nut I36. However, it will be understood that any type of rheostat may be mounted in any desired manner on the control I with its operating shaft projecting upwardly into thebody of the switch as shown in Fig. 2 of th drawings, or the combination of a switch and volume control may be effected in other ways. To prevent ingress of foreign matter into the volume control section 55 and the various contacts, a cover membe I3! is provided which encloses the rheostat 55 and the switch contacts.

The operating shaft I33 of the rheostat is slotted or bifurcated as shown at I38 so as to provide an extensible driving connection with a pin at I33 projecting from side to side through a bore MI in the end of thecontact I01. The extensible connection provided between th bifurcated end of the shaft I33 and the pin I39 permits the contact I01 to be moved longitudinally in the manner explained-above to control the circuits of the conductors 82 and 84.. Rotating the combined knob and button -8 will adjustthe volume of sound emitted by theloud speaker. This is preferably to beaccomplished by foot operation as explained above. The set may be muted at any time in the manner pointed out above irrespective of the angular positionof the rheostat shaft I33.

Figs. 6-8, inclusive, show mechanical means in difierent operating positions for producing a desired control operation of. the. type described above. The mechanical means shown are preferably mounted on the floor board of an automobile for easy actuation by the foot of the driver but may be mounted elsewhere, for example on the steering post for leg, foot or finger operation or on the dashboard for finger operation.

Fig. 6 shows. the mechanical means including a depressible cap I40 in its normal position with switch I35 comprising contacts I42 and I43 in normally open position, while Fig. '7 shows the switch I35 in its closed position and Fig. 8 shows the position of cap I40 after it has been allowed to return to its normal position but before it reaches its normal position and with switch I35 still in its closed position. The switch contact I42 is grounded through the housing I44 while insulated switch contact I43 is connected by lead I51 to the ungrounded terminal of the voice coil of a speaker as shown in Fig. 2 so that when switch I35 is closed the transmission of sound to the speaker is prevented.

The cap I40, having fastened thereto by means of screw I46 the inner flanged hollow cylindrical member I", is normally pressed upwardly .by compression spring I48 to a position where the upturned flange member I49 engages the inwardlyturned edge I50 of the cylindrical housing I44 and limits upward movement of cap I40. Mounted upon member I41 by means of, for example, rivets I 5I is a washer I 52 which has sand.- wiched tightly between member I4! and washer I52 leather packing material I53 with a portion extending therefrom to form a substantially airtight connection between the inner wall .of cylindrical housing I44 andthe outer edge of washer I52 in all positions of the cap I40 and attached washer I52. The inner edge of washer I52 serves an important function as will be described later to produce contact with and movement of the enlarged cylindrical head I54 of combined rod and switch element I42. Mounted upon the base of housing I44 by means of, for example rivets I55, is insulating member I56 having in turn mounted thereon switch contact I43 and lead I51 in sucha manner that a sub-. stantially air tight connection is made atthe base of housing I44. 1

.Washer I52 and insulating member I56 form a seat for the'compression spring I43 whichis substantially stiller than a second compres-- sion spring I58 concentrically mounted therewith in housing I44, spring I 58 exerting in all p0.-

sitions thereof a force between its'seats com-.

prising washer I52 and a flange on rod I42. The housing I44 is preferably fixedly mounted on its supporting member, for example the floor board I of an automobile, and it is seen from the structure thus far described that cap I40 may be moved relative to housing I44 and also that combined rod and contact-member. I42 may. move relative not only to housing I44 but also relative to cap I40 up into the opening I59 in member It is noted also that the chamber I60 enclosed by housing I44 is substantially air tight and that an adjustable needle. valve I6I screwthreadedly mounted on housing I44 furnishes a controllable orifice for the controlled flow of air from the chamber I60 into the atmosphere surrounding chamber I44.

When the cap I40 is depressed by means of, for example the foot of the driver of an automobile from its normal position shown in Fig. 6 to its extreme downward position shown in Fig. 7, the attached washer I52 of course also moves downward, the stiffer spring I 48 is compressed, air is forcibly pressed out of the needle valve I6 I; the switch contact I42 moves downwardly until it engages fixed contact I43, and then further downward movement of the cap I40 requires an additional force andmore than a linear change in force not only to compress spring I48 further but also to begin to compress spring I58, in which case movement of rod or contact I42 is arrested and there is relative movement between member I41 and rod I42 in the opening I59 in which case rod it! approaches its extreme position as shown in Fig. '1. It is thusclear that .an operatoris warned in pressing cap I46 downward of the engagement of switch contact I42 with switch contact I43 by a noticeable change in force required thereafter to move the cap 140 downwardly.

After the control shown in Fig. 7 is released from its extreme position shown therein, the springs I48 and I58 exerta force to move the capiI' IO upwardly, but such upward motion of cap I40 is retarded by thefact'that the needle valve I6I restricts the flow of air and a'partial vacuum exists in chamber I60 due toupwardmotion of the cap, and as a consequence the force of springs I481and I58 acts against an air pressure which may be controlled by adjustment of theneedle valve I6I. When and as the cap I46 moves .upwardly, it is noted that the spring I58 continues to press contact I42 .into engagement with contact I43 with the result that theopening of switch contacts I42, I43 is delayed until the washer I52 moves upwardly asufilcient distance to engage the enlarged head I54 onrod I42 and to move rod I42 upwardly also out of contact with fixed switch contact I43.

It'is thus clear that when'the cap I40 is depressed to its .furthermost position and then released, the switch I35is closed and'remains closed a predetermined time interval whichmay be as muchas one'minute after the cap'is allowed to return to'its normal position under the influence of springs I48 and I58. It is alsoclear that this time interval may be adjusted by adjustment of needle valve I61.

It is also clear that the operator of cap I46 may sense readily, by the sense of touch, the instant contact Ii42 engages contact I43. This feature allows the operator to effect a shorter time interval of closure of switch I35 than the maximum time interval determined by the*open ing in needle valve I6I. Toefiect such a shortened closure of switch I35, the operator simply does not press the cap all the way down after sensing, by the sense or "touch, the closure of switch contacts I42 and. 143. Preferably, inithe operation of the'm'echanical dashpot control described, the cap is pressed all the 'way'down to its extreme position shown in Fig. '7 and then released.

In the modification shown in Fig. 9, the receiver shown in Fig. 2 is muted for a predetermined period or time by pressing the cap I 62 downwardly, for example by the foot, leg or finger of an operator of a vehicle. In Fig. 9, the switch I53, comprising the contacts I64 and [65, finds its counterpart in. Fig. 2 in the switch 69, comprising the contacts '10 and II, and the switch I66 in Fig. 9 comprising the contacts I65 and I6! finds its counterpart in the same switch 69 of Fig. .2, comprising the contacts H and 12. The leads connecting these corresponding switch contacts in Figs. 2 and '9 bear 'the same' reference numerals.

The control of Fig. 9 serves only for producing delayed muting of the type described herein and rendering such delayed muting ineffective in the manner described in connection with the description of Fig. '2. One important feature of the control of Fig. 9 is that it allows the operator to :sense, by his sense of feeling, engagement of contact I64 with contact I65 and the instant delayed muting begins. Further downward 1-2 movement :of :thezcap 2 I62: from its delayed muting position results in contact :between contacts I65 and T61 and rendering inefiectivethe action of associated circuit of 2 in .producing such delayed muting.

The structure of the control shown in Fig. 9 bears some resemblance to the similar control shown in Fig. 2 as will be 'evidentitrom'the fol lowing description.

The switches I63 and 166, the parts of which are shown in section by Fig. '9 of the drawings, include a base'plate I68 to whichis secured'by tubular rivets I68 awafer-dike:contactassembly I19 comprising sheets'of insulating material HI and I12 secured togetherralso by rivets I69. The

I contact member I61 is secured onaprotuberant portion o'fthe metallic strip which is retained between the sheets I'II and ll-2. Ear I13 on the stripprovides a terminal to which the conductor I'M may be integrally secured in a permanently conductive manner "by soldering or welding. The contact tt'Fissecuredon a resilient member such as -a spiral spring I15 which is secured to the insulating'sheet I-TI by means of, for example eyelets.

The cup-shaped contact enclosin'gmember I15 is apertured for connection 'to the base plate I58 by eyelet connections I1 1 or other suitable means. The eyelet connections shown possess the advantage of receiving bolts, screws or-other' connecting means for securing the composite control to the floor board or other part of the vehicle, and also, the control may lie 'closelyin contact with the vehicle floor board or other part. A guide bushing I18 of insulating material is crimped to an aperture I19 located substantially concentrically with'respect to the contacts I64, I55 and I61. The guide bushing I19 serves a three-fold purpose 'in' that it provides an insulating abutment for the contact spring Il'5, serves as a guide for the contact I64 and positions a comparatively powerful contact biasing spring I86. The spring "I presents two substantially flat ends, one of which rests on top of'the member I16 and the other of which reacts against a disc or washer f8I which surrounds the reduced portion 182 of the circular body of the contact actuating rod I63 which has fastened permanently thereto by means of insulating' member I84 the contact I64. Thedi'sc BI preferably has an outside diameter such that it fits 'slidably in the cylindrical housing I85 which has an inwardly turned flange I 85 providing a restricted portion which serves to limit outward movement of the washer I8I and thereby holds the spring I86 partly' compressed. It will be seen from this that the movable contact actuating member I83 is guided for longitudinal movement. At the end of the housing opposite the flange I86 is an outwardly turned flange I81 by means of which the housing is fastened by welding or other suitable means to the top of the contact enclosure member I16. Above the washer IB'I is a cylindrical "sleeve I88. This sleeve is surrounded by another spring I89, which is lighter than the spring I86, and the whole is enclosed by the operating button I 52 which is riveted onto the top of the contact actuating member I83 at I 90. The operating button I62 overlaps the associated housing to prevent dirt and foreign matter from entering the switch body. In this manner the. spring 585 is somewhat compressed under ordinary con ditions. Upon exertion of pressure on the "op; erating button I62 to move the contact I 64 toward circuit closing engagement with the contact I65, the spring I89 is compressed until the inner surface of the button E92 engages the top of the sleeve I88. At this time, the contact 84 is in full circuit closing engagement with the contact its. This completes a circuit. In the circuit of Fig. 2 wherein the control of Fig. 9 is easily substituted by connecting leads of like reference numerals together, the circuit for delayed muting is accomplished. At this point, the contact I65 has not yet engaged the contact I91. Further movement of the operating button I92 must necessarily cause compression of the spring I99 since there is now a direct connection between the button I92, the sleeve I82 and the washer IBI. The added resistance of the heavier spring I89 enables the operator to sense the point at which a first circuit has been closed and the closing of the circuit including contact I6? is about to occur. Upon additional movement of the contact I54, the contact I65, which is now engaged by the contact I64, engages the contact I6? to complete the circuit to be controlled to cut off the period of delayed muting initiated by engagement of contact I94 with contact I65.

It is apparent that when the teachings of the present invention are utilized other mechanical arrangements suggest themselves. For example, mechanisms identical or similar to those found in the so-called fully automatic bread toasters in household use may be utilized. As a further example, as shown in Fig. 10, depression of the control rod I95 which may be attached to one of the depressible control buttons or knobs in the other figures serves to store energy in a coil clock spring I96. Upon release of rod I95 to allow it to assume its normal position shown in Fig. 10, the energy stored in spring I96 not only serves to return control rod I95 to its normal position but serves also to maintain the centrifugally actuated switch I91 comprising contacts I99, I99 inclosed position to ground lead I? connected to the ungrounded terminal of the associated loud speaker for a predetermined time interval in the order of, for example thirty seconds. For this purpose, the rectilinear movement of control rod I95 is converted into rotary movement of shaft 299 by means of the connection between rack 29I and pinion 292. An overrunning clutch designated as 293 which may be a simple pawl and ratchet arrangement serves to rotate weights 294 from the energy stored in clock spring I96 having its free end attached to shaft 299 and its other end permanently fastened in place. Upon rotation above a predetermined speed of weights 294 mounted on a resilient element 296, weights 294 move outwardly from the axis of rotation due to centrifugal forces acting thereon to move the switching disc I99 to the left against cooperating switch contact 298 to close an electrical circuit. The time interval which switch I 91 is thus closed may be adjusted by adjusting the position of contact I98 to control the amount of friction between contacts I98 and I99.

It is clear from the description above that when the control rod I95 is moved downwardly the shaft 299 is rotated, energy is stored in spring I99 but weights 294 are not rotated because of the presence of the overrunning clutch 293. But then, upon release of the control rod I95, the energy stored in spring I95 moves the control rod I95 upward to its normal position, the weights 294 are rotated until substantially all of the energy stored in spring I96 is dissipated as frictional heat in the contacts I98 and I99. It is clear also that shorter times of switch closure than the predetermined times determined by full winding of spring I96 may be produced by moving control rod I downward but not to its most extreme position, in which case the spring I99 .is partly Wound and switch contacts I98, I99 remain closed a much shorter time.

In order to cut short the period of delayed muting or in order to render the action of delayed muting entirely ineffective, the switch 295 may be opened, in which case the associated speaker coil is not short circuited by the delayed muting mechanism described.

While particular embodiments of the present invention have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from this invention in its broader aspects, and, therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of this invention.

I claim:

1. In combination, a normally operative sound amplifying device, a control element movable continuously from its normal position through an intermediate position to a third position, means actuated upon movement of said control element to said intermediate position to render said device inoperative to suitably transmit amplified voltages, said last means having inherent time delay means connected thereto to automatically render said device operative again a substantial time interval after movement to said intermediate position, and means actuated upon movement of said control element to said third position to automatically restore said device to operative position without waiting for the elapse of said time interval.

2. The invention defined in claim 1 characterized by spring means actuated upon movement of said control element allowing an operator thereof to determine, by the sense of feeling, the

position of the control element.

3. The invention defined in claim 1 characterized in that a pair of spring means is operated by said control element, said spring means being of difiering resiliencies thereby allowing an operator to determine by the sense of touch the position of the control element.

4.}The invention defined in claim 1 character- 'ized in that a pair of spring means is operated by said control elements, one of said spring means being compressed upon movement to said intermediate position and said second spring means being compressed upon movement to said third position, thereby allowing an operator to determine by the sense of touch when said control member has reached said intermediate position and is moving from said position to said third position.

I EUGENE F. MCDONALD, JR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,937,173 Taylor Nov. 28, 1933 2,166,532 Naden July 18, 1939 2,197,933 Kirkwood et al Apr. 23, 1940 2,265,394 Ranly Dec. 9, 1941 2,346,177 McDonald, Jr. Apr. 11, 1944 2,389,213 Schwarz Nov. 20, 1945 

